In the past, it has been known that when tumor cells invade out of the blood vessels, vascular endothelial cells rupture. It is also known that neovascularization is deeply involved in the proliferation and migration of cancer and that tumor cells produce and release a variety of neovascularization factors. Especially, neovascularization is considered crucial to the proliferation of solid tumors.
Therefore, a substance that inhibits the neovascularization has the potential to be an anticancer agent that is provided with a novel mode of action. For this reason, several types of neovascularization inhibitory substances such as steroids and metabolic products of microorganisms have already been tested for use. (“Manual for Studies on Cancer Invasion and Metastasis,” The Cancer Metastasis Society Ed., Kinhodo Publisher, 159-182 (1994)). However, it is strongly desired that novel neovascularization inhibitory substances with the action of more effectively inhibiting the proliferation and metastasis of cancers be discovered.